Removal of the innermost portion of the floor of the auditory canal is not always necessary. Sometimes, however, the ‘hypotympanum’ is well marked, and in order to ensure a good result it is wiser to remove this projecting piece of bone. If the ridge of bone be removed piecemeal, and if the gouge or chisel be kept parallel to the floor of the canal, there should be no danger of wounding the bulb of the jugular vein. Cases, however, have been recorded in which this has occurred.
The final step is to see that no pockets nor overhanging ledges or ridges of bone remain, and that all the diseased area has been removed. The cavity, although irregular in outline, should be a continuous one with a smooth surface (Fig. 225).
Wolf’s operation. This slight modification of the Küster-Bergmann operation requires merely a note of description. The position of the patient and the preliminary steps of the operation are the same as in the former operation.
In this operation, instead of first exposing the antrum cavity and afterwards removing the posterior wall of the external meatus, this procedure is performed in one step.
The chisel or gouge is first brought into contact with the bone just behind the upper posterior margin of the auditory canal. The bone is removed in layers by chiselling it away in a forward direction and in such a manner that each stroke of the chisel is carried directly into the auditory canal (Fig. 226). With each successive stroke, begun a little more posterior and inferior to the one preceding it, more bone is removed until at length the antrum is exposed. There should be no risk of injuring the external semicircular canal nor the facial nerve, owing to the fact that the outer wall of the antrum lies superficial to the tympanic cavity and aditus.
After the antrum has been exposed, the technique of the operation is the same as that already described in the Schwartze and Küster-Bergmann operation.
Advantages. 1. If the surgeon be experienced it saves much time, as the preliminary steps of the operation can be carried out very rapidly.
2. If the mastoid be sclerosed and there are no landmarks, the antrum, however small, is bound to be reached by making use of this method, by keeping high up, and, if necessary, exposing the dura mater. To verify the depth to which the bone may be removed and also the position of the antrum, the seeker should be inserted occasionally through the tympanic cavity into the aditus.